By titration it is found that 66.1 mL of 0.125 M NaOH(aq) is needed to neutralize 25.0 mL of HCl(aq). Calculate the concentration of the HCl solution.

mLNaOH x M NaOH = mL HCl x M HCl

calculate the weight of oxalic acid required to neutralise 250 mL , 0.1 N KOH sollution?

To calculate the concentration of the HCl solution, you can use the concept of stoichiometry in a neutralization reaction. The balanced chemical equation for the reaction between NaOH and HCl is:

NaOH(aq) + HCl(aq) -> NaCl(aq) + H2O(l)

According to the equation, the mole ratio between NaOH and HCl is 1:1. This means that for every mole of NaOH used, it will react with one mole of HCl.

First, let's calculate the number of moles of NaOH using its concentration and volume:

moles of NaOH = concentration of NaOH × volume of NaOH
= 0.125 M × 0.0661 L
= 0.0082625 moles

Since the mole ratio between NaOH and HCl is 1:1, the number of moles of HCl can be determined:

moles of HCl = 0.0082625 moles

Next, we can find the concentration of the HCl solution using the moles and volume of HCl:

concentration of HCl = moles of HCl / volume of HCl
= 0.0082625 moles / 0.025 L
= 0.3305 M

Therefore, the concentration of the HCl solution is 0.3305 M.